iMX7 Ethernet - small packets

[urimashiach]

Hello,

I'm using:

* i.MX 7Dual with the Atheros AR8033 Ethernet PHY.

* Linux based on branch imx_4.9.11_1.0.0_ga

The maximum rate for packet length of 64 Byte in UDP is ~36Mbits/sec.

The test is preformed with iperf3:

# iperf3 -c 192.168.11.218 -u -b 0 -l 64 -n 100M -i 10
Connecting to host 192.168.11.218, port 5201
[  4] local 192.168.48.62 port 45709 connected to 192.168.11.218 port 5201
[ ID] Interval           Transfer     Bandwidth       Total Datagrams
[  4]   0.00-10.00  sec  43.3 MBytes  36.3 Mbits/sec  709490  
[  4]  10.00-20.00  sec  43.1 MBytes  36.2 Mbits/sec  706380  
[  4]  20.00-23.17  sec  13.6 MBytes  36.0 Mbits/sec  222530  
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bandwidth       Jitter    Lost/Total Datagrams
[  4]   0.00-23.17  sec   100 MBytes  36.2 Mbits/sec  0.016 ms  44/1638400 (0.0027%)  
[  4] Sent 1638400 datagrams

Much better results for larger packets:

# iperf3 -c 192.168.11.218 -u -b 0 -n 1G -i 10
Connecting to host 192.168.11.218, port 5201
[ 4] local 192.168.48.62 port 33337 connected to 192.168.11.218 port 5201
[ ID] Interval Transfer Bandwidth Total Datagrams
[ 4] 0.00-10.00 sec 645 MBytes 541 Mbits/sec 82570
[ 4] 10.00-15.88 sec 379 MBytes 541 Mbits/sec 48510
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bandwidth Jitter Lost/Total Datagrams
[ 4] 0.00-15.88 sec 1.00 GBytes 541 Mbits/sec 0.069 ms 0/131076 (0%)
[ 4] Sent 131076 datagrams

Is it a driver issue?

Thanks,

Uri

[b36401]

Actually it is normal (and expected) situation when small packets performance is significantly less than big packets.
Maximum efficiency is achieved with largest allowed size.
And in case of minilal size the performance will be less in several times.
Please refer this article for an example values:
http://www.informit.com/articles/article.aspx?p=99812&seqNum=5

Have a great day,
Victor

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[urimashiach]

Hello Victor,

Please note that the article issue is TCP packets while in my question is about a UDP packets.

The acknowledgment is not relevant for UDP communication.

Please note that UDP packets were used in the provided iperf3 tests.

Thanks,

Uri

[b36401]

Anyway it is expected that performance for small packets is significantly less than for big ones.

[Bio_TICFSL]

Hi Uri,

You are limitating the use of 100M and the other is a 1G:

1) iperf3 -c 192.168.11.218 -u -b 0 -l 64 -n 100M -i 10

2) iperf3 -c 192.168.11.218 -u -b 0 -n 1G -i 10

Regards